The startTime property returns the first recorded timestamp of the performance entry.

Note: This feature is available in Web Workers.

The value returned by this property depends on the performance entry's type:

This property is Read only .



Return value

A DOMHighResTimeStamp representing the first timestamp when the performance entry was created.

Note: if the performance entry has an entryType of "resource" (i.e. the entry is a PerformanceResourceTiming object), this property returns the PerformanceEntry.fetchStart timestamp.


The following example shows the use of the startTime property.

function run_PerformanceEntry() {
  log("PerformanceEntry support ...");

  if (performance.mark === undefined) {
    log("... performance.mark Not supported");

  // Create some performance entries via the mark() method

  // Use getEntries() to iterate through the each entry
  var p = performance.getEntries();
  for (var i=0; i < p.length; i++) {
    log("Entry[" + i + "]");
function check_PerformanceEntry(obj) {
  var properties = ["name", "entryType", "startTime", "duration"];
  var methods = ["toJSON"];

  for (var i=0; i < properties.length; i++) {
    // check each property
    var supported = properties[i] in obj;
    if (supported)
      log("..." + properties[i] + " = " + obj[properties[i]]);
      log("..." + properties[i] + " = Not supported");
  for (var i=0; i < methods.length; i++) {
    // check each method
    var supported = typeof obj[methods[i]] == "function";
    if (supported) {
      var js = obj[methods[i]]();
      log("..." + methods[i] + "() = " + JSON.stringify(js));
    } else {
      log("..." + methods[i] + " = Not supported");


Specification Status Comment
Performance Timeline Level 2
The definition of 'startTime' in that specification.
Candidate Recommendation  
Performance Timeline
The definition of 'startTime' in that specification.
Recommendation Initial definition.

Browser compatibility

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support. (Yes) (Yes) (Yes) (Yes) (Yes) No support
Available on workers 62 ? ? ? 49 ?
Feature Android Webview Edge Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile
Basic support. (Yes) (Yes) 25.0 (25.0) 1.2 (25.0) 10.0 (Yes) No support
Avaialable on workers 62 62 ? ? ? 49 ?

Document Tags and Contributors

 Contributors to this page: chrisdavidmills, jpmedley, abbycar, rolfedh, AFBarstow
 Last updated by: chrisdavidmills,